Fabricating microsystems presents a set of challenges distinct from those that exist for manufacturing macroscale devices. Chief among these challenges is the difficulty of manipulating individual objects due to vanishing body forces compared with surface forces. Owing to these challenges, monolithic microfabrication, e.g., layer-by-layer in-situ fabrication of all components using electrochemical processes, is commonly used to fabricate microsystems. However, this approach has substantial drawbacks for the fabrication of non-planar structures, particularly when the integration of heterogeneous materials is desired. For example, complex and lengthy process steps to selectively and precisely deposit and etch materials without damaging those already in place may be required. Even with well-crafted recipes, such fabrication methods have severe limitations in terms of producible geometries and compositions.
Alternatively, pick-and-place microassembly techniques relying on probe tips or microgrippers are capable of assembling separately-fabricated components into microsystems with high flexibility and precision, representing an approach to constructing microsystems that cannot be produced with monolithic microfabrication. However, these approaches traditionally suffer from the difficulty of releasing a retrieved microcomponent on a target location, leading to the involvement of additional strategies including rolling, vibrating, mating, and relying on electrostatic interaction or tacky adhesives.